git-lfs support

Our current bug #2809 (our broken pre-push hook support) led me down the rabbit hole of "what else is required to properly support git-lfs in gitui.

We are looking at basically three things:
1. properly run pre-push hook (thats #2809)
2. hook into filter logic and run them on all checkout-like operations (smudge)
3. hook into filter logic and run them on all worktree->index operations (clean)

Now libgit2 exposes an API to hook into filters but git2-rs does not expose this right now ([open issue](https://github.com/rust-lang/git2-rs/issues/442)).

Since our end goal is to be libgit2 independent I call out whats needed to do this all using gitoxide:

1. we need to migrate all our git-checkout locations to gitoxide
2. migrate all worktree->index operations to gitoxide
3. ~~use gitoxide machinery to hook into filters~~ (turns out gitoxide will already invoke filters for us)
4. ~~forward filter logic via shellout (`git-lfs clean`, `git-lfs smudge` or `git-lfs filter-process`)~~
5. finally we support basic git-lfs
6. add support for more file locking relevant lfs features via hooks: `post-checkout`, `post-merge`, `post-commit`

This issue is more of an epic, I would love to see contributions to take on individual steps as separate PRs.

cc @Byron @cruessler correct me if I am wrong but from the gitoxide side all this is ready to be used or am I wrong?

Further reading: https://github.com/gitui-org/gitui/discussions/1089

Behandle dies als ein Epic und wähle einen unabhängig abgegrenzten Schritt aus, beginnend mit den im Issue beschriebenen checkout-ähnlichen oder worktree-to-index-Operationen. Lies die relevanten gitoxide-Integrationspunkte und überprüfe, wie Filter aufgerufen werden. Ein abgeschlossener Beitrag sollte eine voneinander getrennte Migration oder einen Hook in Richtung grundlegender git-lfs-Unterstützung liefern, wobei sein Verhalten anhand des angegebenen Ziels validiert wird.

Vom Indexierungsmodell aus dem Issue-Text verfasst.